1. Field of the Invention
The invention relates to a projection display apparatus which separates light beams from a light source into red, blue and green light beams. The display apparatus modulates the red, blue and green light beams through light valves provided in a liquid crystal panel in response to image information. The modulated red, blue and green light beams are combined and expansively projected through a projection lens on a projection screen. In particular, the invention relates to a cooling system for efficiently and cleanly cooling the components of a projection display device that separates, modulates combines and projects light beams.
2. Description of Related Art
Conventional projection display devices include an optical unit which optically treats light beams emitted from a light source lamp unit to synthesize a color image in response to image information. The synthesized light beams are projected on a screen through the use of a projection lens unit, a power unit, and a circuit board unit including control circuits and similar devices.
The optical unit separates light beams emitted from the light source lamp unit into red, blue and green color light beams. The optical unit modulates these color light beams with light valves provided in a liquid crystal panel in response to image information. The modulated color light beams are recombined with a cross dichroic prism or similar devices, and are projected on a screen.
Japanese Patent Publications No. 7-225379 discloses a projection display apparatus provided with a polarized light conversion device for aligning the polarization direction of light beams emitted from a light source lamp unit. The polarized light conversion device has a polarized beam splitter array provided with a plurality of sets of polarized light separating films and reflection films which are parallel to each other. The polarized beam splitter array separates incident light beams into two types of straight polarized light components, and aligns the polarization direction of these two types of straight polarized light components.
Some elements of the projection display apparatus, e.g. the polarized light conversion device and the optical unit, are stored in an outer case. A projection side of the projection lens unit is disposed in the outer case such that it protrudes from the front face of the outer case. The outer case is provided with an operating section including a power switch, a light-receiving window for remote control, and an input/output terminal group for sending and receiving signals to and from external devices.
Conventional projection display devices include optical devices in the light source lamp unit, a power unit and an optical unit, all of which are sources of heat. The liquid crystal light valves and their respective polarization plates are major heat sources because they absorb part of the transmitted light beams.
In order to cool the heat sources, the projection display apparatus is provided with a cooling system.
The cooling system introduces fresh air into the outer case through an intake port by a suction fan. The introduced air is circulated through the outer case and exhausted through an air outlet provided on the outer case by an exhaust fan.
In such a cooling system, the power unit, which often become very hot, is provided with a suction fan to introduce the air in the outer case to the interior of the power unit for cooling.
The power unit includes a primary active filter, a power supply, and a ballast. A transmitter FET may be mounted on the circuit board of the primary active filter. A rectifier diode bridge, an oscillating transistor for a D/D converter and a triode regulator for a D/D converter may be mounted on the circuit board of the power supply. Also, devices such as a driving FET for a chopper circuit and a reverse-current preventing diode for a chopper circuit may be mounted on the circuit board of the ballast. Because these devices are heat sources, heat sinks are fixed to them to enhance cooling efficiency. Air introduced with the suction fan cools the heat sinks.
By the time that air is introduced to the power unit in the outer case, it has already been heated by many other elements located in the outer case. Thus, the air introduced to the power unit is hotter than the fresh air introduced into the outer case, and is less efficient in cooling the power unit.
Also, when the air in the outer case is drawn with the suction fan, fresh air containing dust may be introduced through openings of the outer case, e.g., the gap between the projection lens unit and the outer case. As a result, dust may adhere to the optical system and deteriorate the display quality, which reduces the reliability of the apparatus.
The polarized light conversion device is heated because the polarized light separating film and the reflection film absorb some of the incident light. The device has no separate cooling means even though it must be cooled. The polarized light conversion device is therefore cooled by the air circulating from the suction fan to the outlet. Thus, the device may not be efficiently cooled due to insufficient circulation of the cooling air in some apparatus configurations.
It is therefore an object of the invention to provide a projection display apparatus that includes a cooling system that efficiently cools the power unit and polarized light conversion device while preventing airborne debris from contaminating the apparatus.
In accordance with a first embodiment of the invention, a projection display apparatus includes an optical unit for forming an optical image in response to image information by optically treating light beams emitted from a light source lamp unit and for expansively projecting the optical image on a projection area through a projection lens. The projection display device includes a power unit with a ventilating path provided inside the power unit for circulating cooling air. An outer case stores the optical unit and the power unit. The projection display apparatus further includes a cooling air intake port formed on the outer case and a cooling air conducting means for directly conducting fresh air from outside the outer case from the cooling air intake port to the inlet of the ventilating path.
Because the cooling air conducting means directly conducts fresh air to the ventilating path, and because fresh air is cooler than the air in the outer case, the interior of the power unit can be cooled with high efficiency.
A ventilating fan for ventilating the interior of the outer case is preferably provided near the light source lamp unit. The air in the outer case, including the air exhausted from the ventilating path, is collected near the light source lamp unit before being exhausted to the exterior. Thus, the heated light source lamp unit can be securely cooled.
It is preferred that the cooling air conducting means include a duct section connecting the cooling air intake port and the inlet of the ventilating path. Accordingly, the duct section only introduces fresh air from the cooling air intake port to the ventilating path. The duct section also prevents the air from the outer case, which is hotter than the fresh air, from entering into the ventilating path. The interior of the power unit can therefore be more efficiently cooled.
The cooling air conducting means may also include a suction fan provided at the inlet of the ventilating path for drawing fresh air into the ventilating path. A large volume of fresh air can therefore be stably supplied to the ventilating path, and the power unit can be securely cooled with high efficiency.
The duct section securely prevents the suction fan from drawing dust into the outer case through openings in the outer case such as the gap between the projection lens unit and the outer case. Dust can therefore be prevented from adhering onto the optical system, which provides high image display quality and satisfactory reliability.
Although the power unit provided with the suction fan does not have to be located inside the outer case, the optical path from the light source lamp unit to the projection lens unit must be provided within the narrow space in the outer case of the projection display apparatus. The power unit is preferably arranged so that the suction fan is located in the free space in the outer case in order to effectively use the space in the outer case.
The projection lens may be provided so as to have an edge protrude from the outer case. The suction fan may be located on the base end of the projection lens unit, and the cooling air intake port may be formed in a region of a bottom wall of the outer case which includes the lower side of the projection lens unit.
In the optical unit, the projection lens unit may protrude from the light source lamp unit and the optical devices so that the combined light from the optical device is incident on the base end of the projection lens. When the projection lens unit is arranged so as to have a front end protrude from the outer case, a dead space is formed at the side of the base end of the projection lens.
Because the power unit has a suction fan located on the base end of the projection lens unit, the apparatus can be miniaturized as a result of the effective use of space in the outer case.
Further, because the cooling air intake port is formed in a region of the lower side of the projection lens unit, the duct section can be provided in the dead space running from the lower side of the projection lens unit to the side of its base end. Accordingly, space in the outer case is effectively used.
In accordance with another aspect of the invention, a projection display apparatus includes an optical unit including a light source lamp unit and a projection lens unit for forming an optical image in response to image information. The apparatus optically treats light beams emitted from the light source lamp unit and expansively projects the optical image on a projection screen through the projection lens unit. An outer case for storing the optical unit and a power unit includes a ventilating fan for ventilating the interior of the outer case near the light source lamp unit. The projection display apparatus further includes a polarized light conversion device facing an emitting surface of the light source lamp unit for separating the light beams emitted from the light source lamp unit into two types of straight polarized light components and for aligning the polarizing direction of the straight polarized light components. A ventilating path is provided inside the outer case for circulating cooling air along at least one face among a light incident face and a light emerging face of the polarized light conversion device.
Because the ventilating path circulates the cooling air along at least one face among the light incident face and the light emerging face of the polarized light conversion device, the cooling air can securely circulate near the polarized light conversion device to achieve satisfactory cooling effects regardless of the configuration of the apparatus.
A guide is preferably provided for introducing the cooling air circulated along at least one face among the light incident face and light emerging face of the polarized light conversion device to the light source lamp unit.
In such an apparatus, the guide introduces the cooling air after cooling the polarized light conversion device to the light source lamp unit to effectively cool the light source lamp unit. The lamp life is therefore prolonged, and replacement of the lamp is required less frequently.
The outer case may be provided with an operating section having a plurality of switches including a main on/off switch for main power. A protruding section may protrude from the main switch between the main switch and the switch adjacent to the main switch. Such a structure prevents erroneous operation of the main switch.
The protruding section is preferably provided along the periphery of the main switch. This structure also prevents careless contact with the main switch and thus securely prevents erroneous operation of the switch.
A circuit board may be provided in the optical unit. A temperature-sensing element may be connected to the circuit board and located near the light source lamp unit to monitor the temperature of the lamp.
Such a structure effectively monitors the temperature of the light source lamp unit while obviating wiring between the temperature-sensing element and the circuit board because the temperature-sensing element is directly mounted on the circuit board.